Re: [PATCH v4 3/3] PCI: qcom: add support for IPQ60xx PCIe controller

Pali Rohár
2022-01-06T23:54:49Z

On Thursday 06 January 2022 15:20:58 Bjorn Andersson wrote:
> On Thu 06 Jan 10:05 PST 2022, Baruch Siach wrote:
>
> > Hi Lorenzo,
> >
> > On Thu, Jan 06 2022, Lorenzo Pieralisi wrote:
> > > [+Pali - query on reset delay]
> > >
> > > On Mon, Dec 27, 2021 at 08:46:05AM +0200, Baruch Siach wrote:
> > >> From: Selvam Sathappan Periakaruppan <speriaka@codeaurora.org>
> > >>
> > >> IPQ60xx series of SoCs have one port of PCIe gen 3. Add support for that
> > >> platform.
> > >>
> > >> The code is based on downstream[1] Codeaurora kernel v5.4 (branch
> > >> win.linuxopenwrt.2.0).
> > >>
> > >> Split out the DBI registers access part from .init into .post_init. DBI
> > >> registers are only accessible after phy_power_on().
> > >>
> > >> [1] https://source.codeaurora.org/quic/qsdk/oss/kernel/linux-ipq-5.4/
> > >>
> > >> Signed-off-by: Selvam Sathappan Periakaruppan <speriaka@codeaurora.org>
> > >> Signed-off-by: Baruch Siach <baruch.siach@siklu.com>
> > >> ---
> > >> v4:
> > >>
> > >> * Rebase on v5.16-rc1
> > >>
> > >> v3:
> > >> * Drop speed setup; rely on generic code (Rob Herring)
> > >>
> > >> * Drop unused CLK_RATE macros (Bjorn Helgaas)
> > >>
> > >> * Minor formatting fixes (Bjorn Helgaas)
> > >>
> > >> * Add reference to downstream Codeaurora kernel tree (Bjorn Helgaas)
> > >>
> > >> v2:
> > >> * Drop ATU configuration; rely on common code instead
> > >>
> > >> * Use more common register macros
> > >>
> > >> * Use bulk clk and reset APIs
> > >> ---
> > >> drivers/pci/controller/dwc/pcie-designware.h | 1 +
> > >> drivers/pci/controller/dwc/pcie-qcom.c | 145 +++++++++++++++++++
> > >> 2 files changed, 146 insertions(+)
> > >>
> > >> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> > >> index ea87809ee298..279c3778a13b 100644
> > >> --- a/drivers/pci/controller/dwc/pcie-designware.h
> > >> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> > >> @@ -76,6 +76,7 @@
> > >>
> > >> #define GEN3_RELATED_OFF 0x890
> > >> #define GEN3_RELATED_OFF_GEN3_ZRXDC_NONCOMPL BIT(0)
> > >> +#define GEN3_RELATED_OFF_RXEQ_RGRDLESS_RXTS BIT(13)
> > >> #define GEN3_RELATED_OFF_GEN3_EQ_DISABLE BIT(16)
> > >> #define GEN3_RELATED_OFF_RATE_SHADOW_SEL_SHIFT 24
> > >> #define GEN3_RELATED_OFF_RATE_SHADOW_SEL_MASK GENMASK(25, 24)
> > >> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > >> index 1c3d1116bb60..14f86c45a8d9 100644
> > >> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > >> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > >> @@ -52,6 +52,10 @@
> > >> #define PCIE20_PARF_DBI_BASE_ADDR 0x168
> > >> #define PCIE20_PARF_SLV_ADDR_SPACE_SIZE 0x16C
> > >> #define PCIE20_PARF_MHI_CLOCK_RESET_CTRL 0x174
> > >> +#define AHB_CLK_EN BIT(0)
> > >> +#define MSTR_AXI_CLK_EN BIT(1)
> > >> +#define BYPASS BIT(4)
> > >> +
> > >> #define PCIE20_PARF_AXI_MSTR_WR_ADDR_HALT 0x178
> > >> #define PCIE20_PARF_AXI_MSTR_WR_ADDR_HALT_V2 0x1A8
> > >> #define PCIE20_PARF_LTSSM 0x1B0
> > >> @@ -171,6 +175,11 @@ struct qcom_pcie_resources_2_7_0 {
> > >> struct clk *ref_clk_src;
> > >> };
> > >>
> > >> +struct qcom_pcie_resources_2_9_0 {
> > >> + struct clk_bulk_data clks[5];
> > >> + struct reset_control *rst;
> > >> +};
> > >> +
> > >> union qcom_pcie_resources {
> > >> struct qcom_pcie_resources_1_0_0 v1_0_0;
> > >> struct qcom_pcie_resources_2_1_0 v2_1_0;
> > >> @@ -178,6 +187,7 @@ union qcom_pcie_resources {
> > >> struct qcom_pcie_resources_2_3_3 v2_3_3;
> > >> struct qcom_pcie_resources_2_4_0 v2_4_0;
> > >> struct qcom_pcie_resources_2_7_0 v2_7_0;
> > >> + struct qcom_pcie_resources_2_9_0 v2_9_0;
> > >> };
> > >>
> > >> struct qcom_pcie;
> > >> @@ -1297,6 +1307,127 @@ static void qcom_pcie_post_deinit_2_7_0(struct qcom_pcie *pcie)
> > >> clk_disable_unprepare(res->pipe_clk);
> > >> }
> > >>
> > >> +static int qcom_pcie_get_resources_2_9_0(struct qcom_pcie *pcie)
> > >> +{
> > >> + struct qcom_pcie_resources_2_9_0 *res = &pcie->res.v2_9_0;
> > >> + struct dw_pcie *pci = pcie->pci;
> > >> + struct device *dev = pci->dev;
> > >> + int ret;
> > >> +
> > >> + res->clks[0].id = "iface";
> > >> + res->clks[1].id = "axi_m";
> > >> + res->clks[2].id = "axi_s";
> > >> + res->clks[3].id = "axi_bridge";
> > >> + res->clks[4].id = "rchng";
> > >> +
> > >> + ret = devm_clk_bulk_get(dev, ARRAY_SIZE(res->clks), res->clks);
> > >> + if (ret < 0)
> > >> + return ret;
> > >> +
> > >> + res->rst = devm_reset_control_array_get_exclusive(dev);
> > >> + if (IS_ERR(res->rst))
> > >> + return PTR_ERR(res->rst);
> > >> +
> > >> + return 0;
> > >> +}
> > >> +
> > >> +static void qcom_pcie_deinit_2_9_0(struct qcom_pcie *pcie)
> > >> +{
> > >> + struct qcom_pcie_resources_2_9_0 *res = &pcie->res.v2_9_0;
> > >> +
> > >> + clk_bulk_disable_unprepare(ARRAY_SIZE(res->clks), res->clks);
> > >> +}
> > >> +
> > >> +static int qcom_pcie_init_2_9_0(struct qcom_pcie *pcie)
> > >> +{
> > >> + struct qcom_pcie_resources_2_9_0 *res = &pcie->res.v2_9_0;
> > >> + struct device *dev = pcie->pci->dev;
> > >> + int ret;
> > >> +
> > >> + ret = reset_control_assert(res->rst);
> > >> + if (ret) {
> > >> + dev_err(dev, "reset assert failed (%d)\n", ret);
> > >> + return ret;
> > >> + }
> > >> +
> > >> + usleep_range(2000, 2500);
> > >> +
> > >> + ret = reset_control_deassert(res->rst);
> > >> + if (ret) {
> > >> + dev_err(dev, "reset deassert failed (%d)\n", ret);
> > >> + return ret;
> > >> + }
> > >> +
> > >> + /*
> > >> + * Don't have a way to see if the reset has completed.
> > >> + * Wait for some time.
> > >
> > > Is this arbitrary ? What does this reset represent ?
> >
> > I have no idea. I'm just porting working downstream kernel code, and I
> > have no access to hardware documentation.
> >
>
> The reset here doesn't literally reset the device, it will assert (hold)
> the reset line, then sleep 2ms, then deassert (release) it and the sleep
> below will ensure that we don't enable the clocks etc until the hardware
> has been given 2ms to "recover".

Hello! What kind of reset line it asserts? Some internal line to PCIe
controller IP? Or external PCIe Reset line from PCIe controller? Or some
other?

> So it's not a matter of us waiting because we don't know how to check,
> it's a matter of following the datasheet stating the minimum timing of
> the operations to be performed to get the PCIe controller into a known
> (clean) state..

It would be really useful to put comment into code to which datasheet
you are referring and also mention the information that this datasheet
states that timeout of YXZ ms is required.

Lorenzo, added me into this discussion as we found out that lot of PCIe
controller drivers are adding "random" delays into the "random" places
and lot of them just implement required delays defined in PCIe specs.
Something which is common for evert PCIe HW. This starting to be a big
mess as every driver has to reinvent wheel and so all "sleeping code"
should be properly documented. I have an idea of moving PCIe state
machine delays from drivers to PCI core code, but such thing would
require to correctly identify them. And probably there is no better way
than putting comments, why delay is required and why it was chosen to
specific value. If you want to contribute into this idea, look at email:
https://lore.kernel.org/linux-pci/20211022183808.jdeo7vntnagqkg7g@pali/

>
> I'm slightly puzzled to why this matters if the clocks are off, but if
> you're porting downstream code, my suggestion is that you should just
> omit the comment.
>
> > Note that some other variants also add delays before or after reset
> > deassert:
> >
> > qcom_pcie_init_2_4_0()
> >
> > qcom_pcie_init_2_3_3()
> >
> > qcom_pcie_init_2_7_0()
> >
> > baruch
> >
> > >> + */
> > >> + usleep_range(2000, 2500);
> > >> +
> > >> + ret = clk_bulk_prepare_enable(ARRAY_SIZE(res->clks), res->clks);
> > >> + if (ret)
> > >> + goto err_reset;
> > >> +
> > >> + return 0;
> > >> +
> > >> + /*
> > >> + * Not checking for failure, will anyway return
> > >> + * the original failure in 'ret'.
> > >> + */
>
> I think you can omit this comment as well. You failed to enable the
> clocks and you want to inform the caller about that error.
>
> Also, you're asserting the reset line to put the hardware in reset
> again, if that fails there's not much to do.
>
> Regards,
> Bjorn
>
> > >> +err_reset:
> > >> + reset_control_assert(res->rst);
> > >> +
> > >> + return ret;
> > >> +}
> > >> +
> > >> +static int qcom_pcie_post_init_2_9_0(struct qcom_pcie *pcie)
> > >> +{
> > >> + struct dw_pcie *pci = pcie->pci;
> > >> + u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> > >> + u32 val;
> > >> + int i;
> > >> +
> > >> + writel(SLV_ADDR_SPACE_SZ,
> > >> + pcie->parf + PCIE20_v3_PARF_SLV_ADDR_SPACE_SIZE);
> > >> +
> > >> + val = readl(pcie->parf + PCIE20_PARF_PHY_CTRL);
> > >> + val &= ~BIT(0);
> > >> + writel(val, pcie->parf + PCIE20_PARF_PHY_CTRL);
> > >> +
> > >> + writel(0, pcie->parf + PCIE20_PARF_DBI_BASE_ADDR);
> > >> +
> > >> + writel(DEVICE_TYPE_RC, pcie->parf + PCIE20_PARF_DEVICE_TYPE);
> > >> + writel(BYPASS | MSTR_AXI_CLK_EN | AHB_CLK_EN,
> > >> + pcie->parf + PCIE20_PARF_MHI_CLOCK_RESET_CTRL);
> > >> + writel(GEN3_RELATED_OFF_RXEQ_RGRDLESS_RXTS
> > >> + | GEN3_RELATED_OFF_GEN3_ZRXDC_NONCOMPL,
> > >> + pci->dbi_base + GEN3_RELATED_OFF);
> > >> +
> > >> + writel(MST_WAKEUP_EN | SLV_WAKEUP_EN | MSTR_ACLK_CGC_DIS
> > >> + | SLV_ACLK_CGC_DIS | CORE_CLK_CGC_DIS |
> > >> + AUX_PWR_DET | L23_CLK_RMV_DIS | L1_CLK_RMV_DIS,
> > >> + pcie->parf + PCIE20_PARF_SYS_CTRL);
> > >> +
> > >> + writel(0, pcie->parf + PCIE20_PARF_Q2A_FLUSH);
> > >> +
> > >> + dw_pcie_dbi_ro_wr_en(pci);
> > >> + writel(PCIE_CAP_LINK1_VAL, pci->dbi_base + offset + PCI_EXP_SLTCAP);
> > >> +
> > >> + /* Configure PCIe link capabilities for ASPM */
> > >> + val = readl(pci->dbi_base + offset + PCI_EXP_LNKCAP);
> > >> + val &= ~PCI_EXP_LNKCAP_ASPMS;
> > >> + writel(val, pci->dbi_base + offset + PCI_EXP_LNKCAP);
> > >> +
> > >> + writel(PCI_EXP_DEVCTL2_COMP_TMOUT_DIS, pci->dbi_base + offset +
> > >> + PCI_EXP_DEVCTL2);
> > >> +
> > >> + for (i = 0; i < 256; i++)
> > >> + writel(0x0, pcie->parf + PCIE20_PARF_BDF_TO_SID_TABLE_N
> > >> + + (4 * i));
> > >> +
> > >> + return 0;
> > >> +}
> > >> +
> > >> static int qcom_pcie_link_up(struct dw_pcie *pci)
> > >> {
> > >> u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> > >> @@ -1487,6 +1618,15 @@ static const struct qcom_pcie_ops ops_1_9_0 = {
> > >> .config_sid = qcom_pcie_config_sid_sm8250,
> > >> };
> > >>
> > >> +/* Qcom IP rev.: 2.9.0 Synopsys IP rev.: 5.00a */
> > >> +static const struct qcom_pcie_ops ops_2_9_0 = {
> > >> + .get_resources = qcom_pcie_get_resources_2_9_0,
> > >> + .init = qcom_pcie_init_2_9_0,
> > >> + .post_init = qcom_pcie_post_init_2_9_0,
> > >> + .deinit = qcom_pcie_deinit_2_9_0,
> > >> + .ltssm_enable = qcom_pcie_2_3_2_ltssm_enable,
> > >> +};
> > >> +
> > >> static const struct qcom_pcie_cfg apq8084_cfg = {
> > >> .ops = &ops_1_0_0,
> > >> };
> > >> @@ -1520,6 +1660,10 @@ static const struct qcom_pcie_cfg sc7280_cfg = {
> > >> .pipe_clk_need_muxing = true,
> > >> };
> > >>
> > >> +static const struct qcom_pcie_cfg ipq6018_cfg = {
> > >> + .ops = &ops_2_9_0,
> > >> +};
> > >> +
> > >> static const struct dw_pcie_ops dw_pcie_ops = {
> > >> .link_up = qcom_pcie_link_up,
> > >> .start_link = qcom_pcie_start_link,
> > >> @@ -1629,6 +1773,7 @@ static const struct of_device_id qcom_pcie_match[] = {
> > >> { .compatible = "qcom,pcie-sm8250", .data = &sm8250_cfg },
> > >> { .compatible = "qcom,pcie-sc8180x", .data = &sm8250_cfg },
> > >> { .compatible = "qcom,pcie-sc7280", .data = &sc7280_cfg },
> > >> + { .compatible = "qcom,pcie-ipq6018", .data = &ipq6018_cfg },
> > >> { }
> > >> };
> > >>
> > >> --
> > >> 2.34.1
> > >>
> >
> >
> > --
> > ~. .~ Tk Open Systems
> > =}------------------------------------------------ooO--U--Ooo------------{=
> > - baruch@tkos.co.il - tel: +972.52.368.4656, http://www.tkos.co.il -